Self-operating extension flush bolt

ABSTRACT

There is disclosed a self-operating extension flush bolt mechanism for latching the inactive one of a pair of swinging doors, which is operated to latch the door, once the latter is closed, by swinging movement of the other or active door to the closed position. The latch mechanism includes a bolt which is driven home by gear means operated by a cam engageable by the active door. Thermal-responsive means may be provided to inhibit retraction of the bolt when the latter is subjected to high temperatures, as during a fire, such as those likely to cause buckling of the doors.

United States Patent [2 1 Appl. No. [22] Filed [45] Patented [7 3 Assignee [54] SELF-OPERATING EXTENSION FLUSH BOLT 15 Claims, 14 Drawing Figs.

[52] US. Cl 292/58, 292/62, 292/182, 49/394, 292/Dig 66 [51] Int. Cl E05c 5/00 [50] Field of Search 292/4, 22,

1,876,894 9/ 1932 Fitzgerald 70/240 2,034,570 3/1936 Flavin 292/65 FOREIGN PATENTS 250,1 l4 4/ 1926 Great Britain 292/62 500,657 11/1954 Italy 292/62 508,568 1/1955 Italy 292/182 602,708 6/1948 Great Britain 292/182 Primary ExaminerMarvin A. Champion Assistant Examiner-Robert L. Wolfe AttorneyDelio & Montgomery ABSTRACT: There is disclosed a self-operating extension flush bolt mechanism for latching the inactive one of a pair of swinging doors, which is operated to latch the door, once the latter is closed, by swinging movement of the other or active door to the closed position. The latch mechanism includes a bolt which is driven home by gear means operated by a cam engageable by the active door. Thermal-responsive means may be provided to inhibit retraction of the bolt when the latter is subjected to high temperatures, as during a fire, such as those likely to cause buckling of the doors.

PATENTED W1 1 m: 3578.369

SHEET 1 0F 5 INVENTOR.

BY #04; Mad

Jrroeuzy PATENTED Mm 1 I97! sum 3 or 5 wzlfllfld lN-VENTOR. LE0 cbobe s'M/r/l BY J M ama 4 TTOPNE y PATENTEU MAYI 1 IQ'II sum 5 m 5 I!" I I INVENTOR. L 50 COOPERSM/TH c5. fiMM/L IH 'N ATTO/PA/EY SELF-OPERATING EXTENSION FLUSH BOLT BACKGROUND OF THE INVENTION Extension flush bolts are commonly employed in pairs, associated with a pair of swinging doors arranged in side-by-side relation when closed, to latch one of the doors, commonly referred to in the trade as the inactive door, at the top and bottom thereof. The bolts of these latch mechanisms when retracted are flush or substantially flush with the respective upper and lower edges of the inactive door. One latch mechanism of the pair cooperates with a strike located in the door sill or floor while the other cooperates with a strike located in the door frame above the door. The other door of the pair is commonly referred to as the active door. It is commonly carries a central latch mechanism which coacts with a strike associated with the near edge of the inactive door so that the active door may be latched to the inactive door. The latch mechanism of the active door is operated manually as by means of a knob, for example. The latch bolt of the last-mentioned mechanism is commonly spring urged to its latched position to be cammed inwardly by the strike on the inactive door and to thereafter latch thereagainst the active door is closed after the inactive door.

Known prior extension flush bolt mechanisms have all been either of a type requiring manual operation to effect a latched condition and an unlatched condition, or of a type requiring that the active door, on closing subsequent to the closing of the inactive door, engage and actuate trigger means on the near edge of the latter to effect release of spring-biased bolt means to a latched condition. The bolt mechanisms of the lastrnentioned type either require, for movement of the bolt means to the unlatched condition, that the active door be opened and that thereafter manual force is exerted on the inactive door'in an opening direction to retract the bolt means against the aforementioned bias through a camming action of the strike means on the bolt means, or that the bolt means be withdrawn manually after the active door is opened. It will be appreciated from the foregoing that extension flush bolt mechanisms of the last-mentioned type do not have positiveaction bolts, and this is considered a significant drawback, particularly in the use of such mechanisms in association with a pair of swinging fire doors.

Such fire doors, normally held open, are commonly closed by remote control in the event of an emergency such as a fire, and it is highly desirable that on such closing the inactive door he latched by upper and lower self-operating extension flush bolt mechanisms, each having a positive-action bolt. Furthermore, it is desirable that during such an emergency these bolts be maintained in latched condition in a positive manner. Furthermore, it is desirable that the bolt mechanisms of these latches be so constructed that, on opening the active door after the doors have been closed, the bolt of each mechanism on the inactive door be withdrawn without the need of any kind of manipulation or manual effort such as described above. Another need has been the provision of a thermalresponsive lock to prevent retraction of the bolt of a flush-bolt mechanism from the latched condition when the bolt is subjected to high temperatures such as to be likely to cause buckling of the doors or, more specifically, drawing of the active door away from the inactive door.

SUMMARY OF THE INVENTION in accordance with the invention there is provided a selfoperating extension flush bolt having a positive action bolt. The bolt has a positive action in moving to the latched condition thereof and is maintained in latched condition in a positive manner so as to effectively resist forces tending to move the bolt to the unlatched condition during an emergency such as described above. Thermal lock means may be provided to prevent retraction of the bolt from the latched condition as during a fire. There is also provided a bolt which is self-operating in movement of the bolt to the unlatched condition thereof.

More specifically there is provided an extensible and retractable shaft supporting a bolt at one end for movement therewith and rotatable in a support, a bolt-operating cam engageable by the active door, gear means driven by the cam to rotate the shaft, coacting means on the support and the shaft which upon rotation of the shaft through movement of the cam in one direction effects axial movement of the shaft carrying the bolt to extend the latter, and spring means biasing the shaft to a retracted position.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a broken, fragmentary, perspective view of a selfoperating extension flush bolt embodying the invention, show ing the mechanism mounted on a left-hand inactive door at the upper portion thereof, illustrating the bolt thereof in the retracted position;

FIG. 2 is a similar view showing the bolt extended;

FIG. 3 is a broken, side elevational view of the bolt mechanism;

FIG. 4 is a broken top plan view of the bolt mechanism;

FIG. 5 is an enlarged sectional view taken on line 5-5 of FIG. 3;

FIG. 6 is a sectional view taken on line 6-6 of FIG. 4;

FIG. 7 is an enlarged, sectional view taken on line 7-7 of FIG. 3;

FIG. 8 is an enlarged sectional view taken on line 8-8 of FIG. 3;

FIG. 9 is an enlarged sectional view taken on line 9-9 of FIG. 3 and further illustrating the bolt mechanism in association with the inactive door and the active door;

FIG. 10 is a view similar to FIG. 9 but illustrating parts of the bolt mechanism in different positions;

FIG. 11 is an enlarged sectional view taken on line 11-11 of FIG. 3; FIG. 12 is an elevational view in perspective illustrating a typical installation of a pair of the self-operating extension flush bolt mechanisms embodying the invention, these being shown mounted on a right-hand inactive door cooperating with a left-hand active door;

FIG. 13 is a perspective view of the upper bolt-receiving strike mounted on the door frame; and

FIG. 14 is a fragmentary, vertical, sectional view illustrating the bolt in extended position with reference to the door frame and the strike thereon, showing the thermal lock means in operative condition to inhibit retraction of the bolt.

DESCRIPI'ION'OF THE PREFERRED EMBODIMENT There is shown in FIG. 12 in a generally diagrammatic manner a pair of swinging fire doors hingedly supported from a door frame, having the direction of swinging movement indicated and provided with suitable door stop means, not shown. The self-operating extension flush bolt of the invention is especially useful for fire doors of the swinging type but is not limited to use on fire doors. The doors of FIG. 12 when in closed position are located side-by-side and in this illustration the inactive door 10 is the right-hand door and the active door 11 is the left-hand door. The door frame is indicated generally at 12. The active door 11 is provided with a conventional central latch mechanism indicated generally at 13, that is, approximately midway between the upper and lower edges of the active door, which latch mechanism has a spring-biased bolt 14 urged outwardly for cooperation with a conventional strike 15 mounted on the near edge of the inactive door, the arrangement being such that when the inactive door is closed andthe active door is closed thereafter, the latch bolt 14 engages the strike 15 to be cammed inwardly and thereafter is held thereagainst to latch the two doors together. This central latch mechanism may be provided with a conventional operating knob, as shown.

In this view upper and lower self-operating extension flush bolt mechanisms are indicated generally at 16 and 17 respectively. The upper bolt mechanism 16 is operable to extend a bolt through the guide plate 18 mounted on the upper edge of the door to cooperate with a strike indicated generally at I9 mounted on the door frame 12. The lower bolt mechanism 17 is similarly operable to extend a bolt through a similar guide plate, not shown, into a strike indicated generally at 20 shown mounted on a sill 21 but which may be recessed in the floor if desired. The bolt of each extension flush bolt mechanism, to be described in detail hereinafter with reference to other views of the drawings, is operated to be extended by a cam indicated generally at 22 which, when not engaged by the active door Ill, protrudes from the near side edge of the inactive door 10 to the extent indicated. The doors l0 and 11 are shown partially closed.

Normally such fire doors are held in fully open condition by conventional fire protection devices, not shown, and the doors are urged toward their closed positions by conventional door closers, also not shown. As the doors are freed of their fire protection holding devices, usually by remote control, the doors close under the influence of the door closers, the active door 11 being provided with a conventional coordinator, not shown, so that it closes after the inactive door 10. As will be more fully understood hereafter with reference to one of the self-operating extension flush bolts described in detail, the active door 11 on closing engages the cam 22 of each extension flush bolt mechanism, moving the cam inwardly to drive the bolt home into the strike with which it is associated. The active door may be provided with a pair of wear plates 23 secured by screw fasteners for cooperation with the respective ones of the cams 22, and it will be appreciated that these wear plates may be shimmed as necessary to provide the necessary degree of travel of the earns 22. The extension flush bolt mechanisms 16 and 17 are of opposite hands as will be apparent hereinafter.

The door shown in FIGS. I, 2, 9 and 10 on which one of the self-operating extension flush bolts is shown mounted is a lefthand inactive door, the reverse arrangement of doors to that shown in FIG. 12, and the upper bolt mechanism illustrated is of the same hand as the bolt mechanism I7 previously described. A detailed description of this bolt mechanism will be sufficient to understand the construction and operation of the other extension flush bolt mechanism, not shown, of this door, which is of the same hand as the previously described bolt mechanism 16.

The inactive door shown in phantom in FIG. 1 is indicated generally at 25'and cooperates with an active door 26 similarly shown in FIGS. 9 and 10. The upper self-operating extension flush bolt of FIG. 1 comprises an elongated base 27 (FIG. 1) which may be formed as a metal casting having as a part thereof a flange forming a plate 28 (FIG. 6) for attachment to the inside side margin of the door 25 through conventional fastener-receiving openings. A thin cap 29 may be used for trim purposes in overlying relation to the plate 28 having fastener-receiving openings alignable with the last-mentioned openings in the plate. The base 27 in the central region thereof has an outstanding block part 30 and spaced longitudinally from the latter a block part 31 as shown in the last-mentioned view. Extending longitudinally of the base through the block part 30 is a bore 32 concentric with a similar but somewhat smaller bore 33 extending through the block 31.

As best shown in FIGS. 7 and 8 the base 27 in the central region thereof has a generally rectangular recess 34 in one side thereof which has a central extension 35 extending transversely of the base 27. A pair of spaced-apart bearing blocks 36 are mounted in the recess 34 and secured to the base 27 as by screws 37 to support therebetween and extending longitudinally of the base 27 a pivot pin 38 for the aforementioned cam 22 disposed between the bearing blocks 36 and extending into the aforementioned recess 34 and the extension 35 thereof as shown in the last-mentioned views. The cam 22 is of platelike form and, as shown, is relatively thick. Both bearing blocks 36 may be formed of sintered stainless steel and the cam 22 may be formed of oil-impregnated sintered stainless steel. The base 27 may be formed of oil-impregnated sintered brass. As indicated in FIGS. 7 and 8, each bearing block 36 may have a lug 39 extending into a notch in the base 27 to prevent angular movement of the bearing block 36 with reference to the base 27 The cam 22 on the pivot 38 has an inclined face 40 for engagement with the active door 26 or, more specially, the wear plate 23 thereon. Formed on a radius of the pivotal axis of the cam 22 are a series of gear teeth 41, the arrangement being such that the cam 22 has as an integral part thereof a gear segment which is shown to advantage in FIGS. 9 and I0.

A shaft 43 is supported in the block 31 of the base by the bore 33 formed therein in which the shaft is rotatable and axially extensible. The shaft 43 has a reduced tail portion 44 (FIG. 10) on which a longitudinal element 45 of U-shape in cross section is keyed and secured thereto by pins 46. Intermediate the legs thereof the U-shaped element 45 has on its periphery a series of gear teeth 47 which mesh with the gear teeth 41 provided on the cam 22. The arrangement is such that the gear segment 45 may be rotated on angular movement of the cam 22 on its pivotal axis while being movable axially with the shaft 43 with reference to the cam having the aforementioned gear teeth thereon. As shown the gear teeth 47 have a much longer axial dimension than the gear teeth 41 with which the former are slidable.

A shaft section 48 is angularly fixed with reference to the shaft 43 at the rear end thereof for support in the bore 32 of the block 30, the arrangement being such that the shaft sec tion 48 is supported for axial and rotary movement. The shaft section 48 has a central longitudinal bore 49 therethrough enlarged by a counterbore 50 at its rear end. A shouldered retaining shaft 51 extends through the bore 49 and has at its forward end a threaded portion threaded into a tapped hole 52 in the rear end of the shaft 43. A shoulder 53 of the retaining shaft 51 bottoms in the counterbore 50 of the shaft section 48 to secure the shaft section with the shaft 43 and the shaft 48 at its forward end is keyed to the rear end of the shaft 43 to prevent angular movement therebetween. In the illustrated form the retaining shaft 51 is assembled with the gear segment 45 prior to the driving of the pins 46 and the arrangement of the last-mentioned pins is such that when one of the latter is driven, it prevents removal of the retaining shaft thereafter until the pin has been removed.

It will be noted that the shaft section 48 is of somewhat larger diameter than the shaft 43. In effect the shaft section 48 is an integral part of the shaft 43 as is the retaining shaft 51.

To effect axial movement. of the shaft 43 on swinging movement of the cam 22 in a direction to drive the gear segment 45 through the teeth on the cam, coacting means are provided on the block 30 and the shaft section 48 to move the shaft to the right as viewed in FIG. 6. In the form illustrated by way of example, this coacting means takes the form of three pins 55 driven into the block 30 so as to extend into the bore 32 thereof and into helical tracks 56 (FIG. 11) formed in the shaft section 48. The tracks are formed as grooves and the pitch is quite steep.

A light helical spring 57 is provided urging the shaft 43 from its extended position of FIG. 2 to the retracted position of FIGS. 1 and 6. To support the spring 57 which embraces the shaft section 48 and has one end thereof abutting the block 30, the tail end of the retaining shaft 51 is threaded as at 58, and this threaded portion of the shaft, notched at its rear end to receive the blade of a tool such as a screw driver, extends through the bottom of a cup element 59 having a radially outwardly extending lip 60 against which the other end of the spring 57 abuts, the cup being retained on the shaft 51 by a nut 61 adjustable receiving the threaded portion 58 of the retaining shaft, which nut bottoms in the cup element 59. The spring 57 is compressed between the cup 59 and the block 30 so as to constantly urge the shaft 43 toward the left as viewed in FIG. 6 or in a downward direction as viewed in FIG. 1. It is to be understood that the steep pitch of the helical tracks 56 in the shaft section 48 permits this shaft-retracting action of the spring 57.

As viewed in FIGS. 1 and 2, the upper end of the shaft 43 carries the bolt head indicated generally at '63. The bolt head may be considered an integral part of the shaft 43. However, in the form illustrated by way of example, the bolt head is connected to the shaft through a rod 64. One end of the rod 64 is received in a longitudinal blind hole 65 formed in the forward end of the shaft 43. Adjacent the forward end of the shaft 43 the shaft is provided with a transversely extending groove 66 in communication with the hole 65. The rear end portion of the shaft 64 has a circumferential groove 67 and a spring clip 68 extends into the groove 66 of the shaft 43 and into the groove 67 in the rod 64 to lock the rod and shaft together. However, there may be some articulation between these parts if desired thoughthey remain secured together by the spring clip 68. The clip 68 acts as an abutment engageable with the block 31 to limit travel of the shaft 43 on retraction of the latter. It may be noted here that the gear segment 45 is engageable with the block 31 on extension of the shaft 43 to limit the travel of the shaft 43 in this direction.

The bolt head 63 of the illustrated cross section is preferably formed of oil-impregnated powdered metal. It has a central longitudinal bore 70 extending therethrough (FIG. 5) and counterbored at the rear end. The rod 64, stepped at its forward end, extends through this bore in the bolt head as best shown in FIG. 5. The bolt head 63 at diametrically opposite locations has longitudinal grooves 71 formed therein which are flat bottomed and of a depth more than sufficient to receive therein, in the illustrated form of the invention, end portions of a thermal bimetallic strip element 72 of U-shape, which end portions of the strip are indicated at 73. These end portions may be considered arms or legs. Also as shown in the lastmentioned view the rod 64 extends through a hole in the strip 72 formed midway between its ends and through a washer, and the forward or outer end of the rod 64 is spun over to secure the whole together.

The bolt head 63 slides in a guide plate 18 secured to the upper edge of the door 25 as by screw fasteners 77, as shown in FIG. 1. For this purpose the plate 18 is provided with a round hole 78 slidable receiving the bolt head. As shown in the last-mentioned view, when the bolt is retracted the upper end of the bolt head 63 rests in the hole 78 in the guide plate.

As shown in FIG. 2, on extension of the bolt head with the shaft 43 the bolt head is projected beyond the guide plate 18, the distance of projection preferably being about 1 inch, and during this movement enters the strike 19 having a central bolt-receiving aperture therein 79 which may be somewhat elongated, as shown, in a direction lengthwise of the upper edge of the door to insure reception of the bolt therein without exact alignment of the strike 19 with the bolt, the strike 19 being of platelike form and being secured to the door frame above the door by suitable screw fasteners 80 extending therethrough as shown in FIG. 13.

The operation of the extension flush bolt mechanism will be evident from the foregoing description of its construction. When the active door is not closed against the inactive door, as shown in FIG. 9, the operating cam 22 of the mechanism has the angular relationship shown in the last-mentioned view and protrudes from the inactive door 25 to the extent indicated, presenting the inclined cam surface 40 for cooperation with the active door 26. As the active door 26 moves from the position of FIG. 9 to the closed position of FIG. 10, it ef' fects by engagement therewith angular movement of the cam 22 to the position shown in the last-mentioned view in which it is almost flush with the inactive door 25 but protrudes slightly therefrom. It will be understood from the foregoing that movement of the cam 22 to the last-mentioned position drives the shaft 43 through the gear segment 45 fixed thereto and coacting with the gear teeth on the cam 22. As previously described, this rotary movement of the shaft effects, through its tail section 48 having cam track means 56 coacting with cam pins 55 fixed to the support 27, axial movement of the shaft together with the bolt head 63 to drive the latter home in the strike in a positive manner,

It will also be understood that while the active door 26 is closed and the operating cam 22 is maintained thereby in the angular position shown in FIG. 10, the bolt is maintained positively in latched condition. However, when the active door 26 is thereafter opened, the extension flush bolt mechanism is self-operated to return to the unlatched condition, the spring 57 biasing the bolt in a retracting direction and effecting through the cam pins 55 extending into the cam tracks 56 rotary movement of the shaft including the tail portion 44 thereof to return the gear segment 45 and the cam 22 carrying the gear teeth 41 to the positions shown in FIG. 9.

The thermal-responsive device for preventing retraction of the latch bolt 63 and including the aforementioned U-shaped bimetallic strip 72 is shown in operative condition in FIG. 14 illustrated in association with the door 10 of FIG. I2 and the door frame 12. The aforementioned construction and arrangement of the thermal-responsive element including the bimetallic strip 72 is such that as the environment of the bimetallic strip 72 reaches a temperature of, say, to F. as during a fire when the doors IOand 11 are closed and the inactive door is latched as aforesaid, the arms 73 of the bimetallic strip 72 spread apart so that their distal ends move out of the grooves 71 in the bolt head to overlap the guide plate 18 secured to the door 10 at its upper edge to thereby prevent retraction of the bolt until the ambient temperature has cooled sufficiently to permit the arms 73 to return within the grooves 71 in the bolt head 63. This means that should the active door buckle, for example, under extremely high tempera tures caused by a fire, in a manner to pull away from or become separated from the operating cam 22 of the extension flush bolt mechanism, the latch bolt will remain in its operative latched condition until the bimetallic element has been permitted by cooling of the surrounding atmosphere to return to its normal position in which the arms 73 are retracted within the bolt head 63.

It will be apparent from the foregoing that the invention may be embodied in a flush bolt mechanism which is not of the extension type. That is, it may be embodied in a bolt mechanism which is mounted nearer to the bolt-receiving strike, without the rod 64 separating the shaft 43 from the bolt head 63 and in a mechanism in which the bolt head is an integral part of the shaft.

It will also be apparent from the foregoing that the thermalresponsive element to prevent retraction of the bolt under the circumstances outlined above need not take the form of the U- shaped element 72. It may, for example, comprise a bimetallic member including a movable arm normally disposed longitudinally of the bolt, one end of which is in fixed relation to the bolt and having a free end extensible with the bolt past a sta' tionary element such as a portion of the strike, for example, and which on being subjected to high environmental temperatures bends outwardly from the bolt to provide an abutment engageable with the last-mentioned stationary element to prevent retraction of the bolt.

While only one form of the extension flush bolt has been shown in the drawings and described above, it will be apparent to those versed in the art that the invention may take other forms without departing from the principles of the invention.

Iclaim:

1. In a self-operating flush bolt mechanism for latching the inactive one of a pair of swinging doors, which is operated to latch the door, once the latter is closed, by swinging move ment of the other or inactive door to the closed position, a support adapted to be mounted on the inactive door, an extensible and retractable shaft rotatable in said support and including a latch bolt at one end thereof, boltoperating means comprising a cam for engagement by the active door mounted for swinging movement on said support, gear means driven by the cam to rotate said shaft, and means intermediate the support and the shaft which upon rotation of the shaft in one direction effects positive axial movement of the shaft and bolt to extend the latter to latched position.

2. A self-operating flush bolt mechanism as defined in claim 1 wherein said bolt-operating means comprises spring means operative to retract the bolt to unlatched position on disengagement of said cam when the active door is opened.

3. A self-operating flush bolt mechanism as defined in claim 1, wherein said cam has a toothed portion and said gear means comprises a gear member fixed to said shaft so as to be axially movable therewith and meshing with said toothed portion of the cam.

i. A self-operating flush bolt mechanism as defined in claim ll wherein said bolt-operating means comprises spring means operative to retract the bolt to unlatched position on disengagement of said cam when the active door is opened, said cam having a toothed portion, said gear means comprising a gear member fixed to said shaft so as to be axially movable therewith and meshing with said toothed portion of the cam, said cam being mounted for nontranslatory movement.

5. A self-operating flush bolt mechanism as defined in claim l wherein said bolt'operating means comprises spring means operative to retract the'bolt to the unlatched position on disengagement of said cam when the active door is opened, said means intermediate the shaft and the support for effecting axial movement of the shaft in a bolt-latching direction comprising helical cam track means on the shaft engaged by pin means on the support.

6. A self-operating flush bolt mechanism as defined in claim ll wherein a guide element in provided for the bolt adapted to be fixed to the inactive door and in which the bolt is slidable, and a strike is provided having an element for reception of the bolt and adapted to be fixed to the doorframe, and wherein a bimetallic member is provided having a movable arm normally disposed longitudinally of the bolt, one end of which is in fixed relation to the bolt and having a free end extensible with the bolt past one of said elements and which on being subjected to high environmental temperatures bends outwardly from the bolt to provide an abutment engageable with the last-mentioned one of said elements to prevent retraction of the bolt.

7. A self-operating flush bolt mechanism as defined in claim 1 wherein said means intermediate the shaft and the support for effecting axial movement of the shaft in a bolt-latching direction comprises coacting cam means on the shaft and the support.

8. A self-operating flush bolt mechanism as defined in claim 3 wherein said cam is mounted for nontranslatory movement.

9. A self-operating flush bolt mechanism as defined in claim I wherein said coacting cam means on the shaft and the support comprises helical track means on the shaft engaged by pin means on the support.

10. In a bolt mechanism having a strike, a support, a movable bolt in the support extensible into the strike, the improvement comprising a stationary guide element for the bolt in which element the bolt is slidable, the strike having a fixed element thereon, and a bimetallic member having a movable arm normally disposed longitudinally of the bolt, one end of which is in fixed relation to the bolt and having a free end extensible with the bolt past one of said elements and which on being subjected to high environmental temperatures bends outwardly from the bolt to provide an abutment engageable with the last-mentioned one of said elements to prevent retraction of the bolt.

11. For use in conjunction with a pair of swinging doors, a bolt mechanism comprising a support member having a surface adapted to be mounted essentially flush with the free edge of one of a pair of the doors, shaft support means extend ingfrom said support member, a shaft slidable carried by said support means and including a latch bolt at one end thereof, a cam pivotally carried by said support member and extending beyond said face thereof and adapted to be engaged by the other of the swinging doors, gear means, said cam arranged to engage and rotate said gear means, and means on said shaft responsive to rotation of said gear means for imparting linear movement to said shaft.

12. The mechanism of claim 11 wherein said shaft has said gear means carried thereon and said cam means has teeth thereon engaging said gear means,

13. The mechanism of claim 11 further including a spring acting on said shaft to return said shaft when said cam is disengaged by said other of the doors.

14. The mechanism of claim 11 wherein said means for imparting linear motion comprises a helical groove on said shaft, a pin carried by said support member extending into said groove.

ll5. For use in conjunction with a pair of swinging doors, a bolt mechanism comprising a support member having a surface adapted to be mounted essentially flush with the free edge of one of a pair of swinging doors, shaft support means extending from said support member on the side thereof opposite said surface, a shaft slidably carried by said support means and including a latch bolt at one end thereof adapted to be extended beyond a horizontal edge of the door, spring means normally biasing said shaft to a retracted position, a cam pivotally carried by said support member and extending beyond the face thereof and adapted to be engaged by the other of the swinging doors, gear means, said cam arranged to engage and rotate said gear means and impart linear movement to said shaft to move said latch bolt behind the horizontal edge against the bias of said spring.

Eggs?" UNI'I'I'II) S'IA'I'I'IH I'A'II'IN'I' OFFICE CERTIFICATE OF CORRECTION Patent No. 3,578,369 Dated May 11, 1971 Inventor) Leo Coopersmith It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 15, delete "is" (second occurr ence). Line 23, after "thereagainst" insert as Column l, line 68, delete "adjustable" and insert adjustably Column 7, line 27, after "element" delete "in" and insert is Column 8, line &7, delete "behind" and insert beyond Signed and sealed this 16th day of November 1971.

(SEAL) Attsst:

EDWARD M.FLETCH.E'R, JR. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patents 

1. In a self-operating flush bolt mechanism for latching the inactive one of a pair of swinging doors, which is operated to latch the door, once the latter is closed, by swinging movement of the other or inactive door to the closed position, a support adapted to be mounted on the inactive door, an extensible and retractable shaft rotatable in said support and including a latch bolt at one end thereof, bolt-operating means comprising a cam for engagement by the active door mounted for swinging movement on said support, gear means driven by the cam to rotate said shaft, and means intermediate the support and the shaft which upon rotation of the shaft in one direction effects positive axial movement of the shaft and bolt to extend the latter to latched position.
 2. A self-operating flush bolt mechanism as defined in claim 1 wherein said bolt-operating means comprises spring means operative to retract the bolt to unlatched position on disengagement of said cam when the active door is opened.
 3. A self-operating flush bolt mechanism as defined in claim 1, wherein said cam has a toothed portion and said gear means comprises a gear member fixed to said shaft so as to be axially movable therewith and meshing with said toothed portion of the cam.
 4. A self-operating flush bolt mechanism as defined in claim 1 wherein said bolt-operating means comprises spring means operative to retract the bolt to unlatched position on disengagement of said cam when the active door is opened, said cam having a toothed portion, said gear means comprising a gear member fixed to said shaft so as to be axially movable therewith and meshing with said toothed portion of the cam, said cam being mounted for nontranslatory movement.
 5. A self-operating flush bolt mechanism as defined in claim 1 wherein said bolt-operating means comprises spring means operative to retract the bolt to the unlatched position on disengagement of said cam when the active door is opened, said means intermediate the shaft and the support for effecting axial movement of the shaft in a bolt-latching direction comprising helical cam track means on the shaft engaged by pin means on the support.
 6. A self-operating flush bolt mechanism as defined in claim 1 wherein a guide element in provided for the bolt adapted to be fixed to the inactive door and in which the bolt is slidable, and a strike is provided having an element for reception of the bolt and adapted to be fixed to the doorframe, and wherein a bimetallic member is provided having a movable arm normally disposed longitudinally of the bolt, one end of which is in fixed relation to the bolt and having a free end extensible with the bolt past one of said elements and which on being subjected to high environmental temperatures bends outwardly from the bolt to provide an abutment engageable with the last-mentioned one of said elements to prevent retraction of the bolt.
 7. A self-operating flush bolt mechanism as defined in claim 1 wherein said means intermediate the shaft and the support for effecting axial movement of the shaft in a bolt-latching direction comprises coacting cam means on the shaft and the support.
 8. A self-operating flush bolt mechanism as defined in claim 3 wherein said cam is mounted for nontranslatory movement.
 9. A self-operating flush bolt mechanism as defined in claim 7 wherein said coacting cam means on the shaft and the support comprises helical track means on the shaft engaged by pin means on the support.
 10. In a bolt mechanism having a strike, a support, a movable bolt in the support extensible into the strike, the improvement comprising a stationary guide element for the bolt in which element the bolt is slidable, the strike having a fixed element thereon, and a bimetallic member having a movable arm normally disposed longitudinally of the bolt, one end of which is in fixed relation to the bolt and having a free end extensible with the bolt past one of said elements and which on being subjected to high environmental temperatures bends outwardly from the bolt to provide an abutment engageable with the last-mentioned one of said elements to prevent retraction of the bolt.
 11. For use in conjunction with a pair of swinging doors, a bolt mechanism comprising a support member having a surface adapted to be mounted essentially flush with the free edge of one of a pair of the doors, shaft support means extending from said support member, a shaft slidable carried by said support means and including a latch bolt at one end thereof, a cam pivotally carried by said support member and extending beyond said face thereof and adapted to be engaged by the other of the swinging doors, gear means, said cam arranged to engage and rotate said gear means, and means on said shaft responsive to rotation of said gear means for imparting linear movement to said shaft.
 12. The mechanism of claim 11 wherein said shaft has said gear means carried thereon and said cam means has teeth thereon engaging said gear means,
 13. The mechanism of claim 11 further including a spring acting on said shaft to return said shaft when said cam is disengaged by said other of the doors.
 14. The mechanism of claim 11 wherein said means for imparting linear motion comprises a helical groove on said shaft, a pin carried by said support member extending into said groove.
 15. For use in conjunction with a pair of swinging doors, a bolt mechanism comprising a support member having a surface adapted to be mounted essentially flush with the free edge of one of a pair of swinging doors, shaft support means extending from said support member on the side thereof opposite said surface, a shaft slidably carried by said support means and including a latch bolt at one end thereof adapted to be extended beyond a horizontal edge of the door, spring means normally biasing said shaft to a retracted position, a cam pivotally carried by said support member and extending beyond the face thereof and adapted to be engaged by the other of the swinging doors, gear means, said cam arranged to engage and rotate said gear means and impart linear movement to said shaft to move said latch bolt behind the horizontal edge against the bias of said spring. 